MS11-L MOS memory

MS11-L board

The MS11-L was final UNIBUS main memory from DEC; a single card can hold enough MOS DRAM chips to fill the entire UNIBUS address space. It had a jumper option to enable use on an Extended UNIBUS. Configuration is by DIP switches. It used on-board parity for error detection.

Fully populated with 16Kx1 chips, it is known as the MS11-LD, and holds 256K bytes. The quarter-, half- and three-quarter-populated versions are the MS11-LA, -LB and -LC, respectively; with 64KB, 128KB and 192KB.

It plugs into a MUD backplane (only; not SPC). It is a single hex card, the M7891, so it cannot go in the end slots of the backplane.

The access time is 385 nsec (typical; 1025 nsec maximum on refresh conflict), and the cycle time is 510 nsec (1050 nsec maximum on refresh conflict). Refresh time is 570 nsec (typical; 610 nsec maximum); the time for a complete refresh pass is 14.5 μsec (typical), 13.5 μsec (minimum).

It can use either +/-15V or +/-12V to power the memory chips (in some MUD slots, the 15V pins provide 12V). The board has provision to use battery backup power to retain data during a power outage. Power requirements are 1.5-1.8A of +5V, 1-1.3A of +5VBB, 9-20mA of -12/-15V (depending on size, i.e. number of MOS memory chips), and 485-700 mA of +12/+15 (when active; depending on size).